Q: 3 lan ports is not enough

but 3 ports lan is not enough. Can i use a  any specificatios?

You can add an Ethernet switch if you need more connections. They come in 5-port, 8-port, 16-port, etc versions.

Something like this, for example:

http://www.bestbuy.com/site/Networking/Hubs-Switches/abcat0503012.c?id=abcat0503 012

my houve is big and i want to extend the wifi. Can i extend win another AP extreme by ethernet, so i cant lose sinal strengh?

Yes. Apple has instructions to do this here:

http://support.apple.com/kb/HT4259